Ring opening of cyclopropylmethylidene with trimethylaluminum: Synthesis of 1-cyclopropylethyl ether as an acid labile protecting group for hydroxyl Protection and carbohydrate synthesis

The 4,6-<i>O</i>-cyclopropylmethylidene (CPMD) moiety of a methyl α-glucoside derivative can be regioselectively opened by trimethylaluminum to afford a corresponding 1-cyclopropylethyl (CPE) ether at C4 and a free alcohol at C6. This 1-CPE ether was found to be an acid-labile hydroxyl protecting group and can be readily cleaved using 10% trifluoracetic acid in dichloromethane at room temperature. The utilization of 1-CPE ether as a hydroxyl protecting group has been demonstrated in the efficient synthesis of a trisaccharide.